Measuring a differential signal with the use of an oscilloscope is a familiar task in development laboratories and test stations. In order to register the two partial signals of the differential signal, a sensor with two test-contact probes is used, which each register one partial signal and route it to the oscilloscope for further signal processing and display on a screen.
Since the two test-contact points, at which the two partial signals of the differential signal are registered with the sensor, provide a certain spacing distance on the printed circuit board which can differentiate between the individual measurements of different differential signals on a printed circuit board, a sensor is required, with which the spacing distance between the two test-contact probes can be matched to the different spacing distance between two test-contact points.
A sensor of this kind, of which the test-contact probes can be adjusted to different spacing distances from one another, is known from U.S. Pat. No. 7,102,370 B1. For this purpose, the sensor in the embodiment illustrated in FIG. 6 provides two rotary elements capable of being rotated relative to one another, which are each connected to a test-contact probe arranged eccentrically with reference to its axis of rotation.
With a technical embodiment of this kind of a sensor, a slip can occur under some circumstances at the contact points between the two rotary elements rotatable relative to one another. When the user of the sensor wishes to adjust the spacing distance between the two test-contact probes, this slip disadvantageously leads to a non-simultaneous rotation of the rotary elements about their own axes of rotation and accordingly determines a non-symmetrical position change of the two test-contact elements. Moreover, as a result of the slip, it cannot be guaranteed with a sensor of this kind, that the two test-contact elements will necessarily remain at the spacing distance set by the user.
What is needed, therefore, is a sensor for measuring a differential signal, which, on the one hand, guarantees a simultaneous, symmetrical position adjustment of the two test-contact elements as required by the user and, on the other hand, guarantees that the two test contact elements remain at the spacing distance set by the user.